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Main Authors: Jasny, Ethan, Kenny, Christopher T., McCartan, Cory, Simko, Tyler, Wu, Melissa, Zhao, Michael Y., Arora, Aneetej, Ebowe, Emma, O'Sullivan, Philip, Samarth, Taran, Imai, Kosuke
Format: Preprint
Published: 2025
Subjects:
Online Access:https://arxiv.org/abs/2508.15885
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author Jasny, Ethan
Kenny, Christopher T.
McCartan, Cory
Simko, Tyler
Wu, Melissa
Zhao, Michael Y.
Arora, Aneetej
Ebowe, Emma
O'Sullivan, Philip
Samarth, Taran
Imai, Kosuke
author_facet Jasny, Ethan
Kenny, Christopher T.
McCartan, Cory
Simko, Tyler
Wu, Melissa
Zhao, Michael Y.
Arora, Aneetej
Ebowe, Emma
O'Sullivan, Philip
Samarth, Taran
Imai, Kosuke
contents Changes in political geography and electoral district boundaries shape representation in the United States Congress. To disentangle the effects of geography and gerrymandering, we generate a large ensemble of alternative redistricting plans that follow each state's legal criteria. Comparing enacted plans to these simulations reveals partisan bias, while changes in the simulated plans over time identify shifts in political geography. Our analysis shows that geographic polarization has intensified between 2010 and 2020: Republicans improved their standing in rural and rural-suburban areas, while Democrats further gained in urban districts. These shifts offset nationally, reducing the Republican geographic advantage from 14 to 10 seats. Additionally, pro-Democratic gerrymandering in 2020 counteracted earlier Republican efforts, reducing the GOP redistricting advantage by two seats. In total, the pro-Republican bias declined from 16 to 10 seats. Crucially, shifts in political geography and gerrymandering reduced the number of highly competitive districts by over 25%, with geographic polarization driving most of the decline.
format Preprint
id arxiv_https___arxiv_org_abs_2508_15885
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Gerrymandering and geographic polarization have reduced electoral competition
Jasny, Ethan
Kenny, Christopher T.
McCartan, Cory
Simko, Tyler
Wu, Melissa
Zhao, Michael Y.
Arora, Aneetej
Ebowe, Emma
O'Sullivan, Philip
Samarth, Taran
Imai, Kosuke
Applications
Changes in political geography and electoral district boundaries shape representation in the United States Congress. To disentangle the effects of geography and gerrymandering, we generate a large ensemble of alternative redistricting plans that follow each state's legal criteria. Comparing enacted plans to these simulations reveals partisan bias, while changes in the simulated plans over time identify shifts in political geography. Our analysis shows that geographic polarization has intensified between 2010 and 2020: Republicans improved their standing in rural and rural-suburban areas, while Democrats further gained in urban districts. These shifts offset nationally, reducing the Republican geographic advantage from 14 to 10 seats. Additionally, pro-Democratic gerrymandering in 2020 counteracted earlier Republican efforts, reducing the GOP redistricting advantage by two seats. In total, the pro-Republican bias declined from 16 to 10 seats. Crucially, shifts in political geography and gerrymandering reduced the number of highly competitive districts by over 25%, with geographic polarization driving most of the decline.
title Gerrymandering and geographic polarization have reduced electoral competition
topic Applications
url https://arxiv.org/abs/2508.15885